It is known that marine organisms comprising shells such as acorn shell and blue mussel and algae adhered to a ship floating on the sea lead to an increase in seawater resistance to the movement of the ship, so that the sailing speed considerably lowers. In addition, the adhered marine organisms become a cause of corrosion of the ship body. Due to these reasons, the removal of the adhered marine organisms is very important work to save fuel cost required for the movement of the ship, and provide safe voyage.
In the past, various kinds of approaches have been proposed to prevent the adherence of marine organisms. For example, Japanese Patent Early publication No. 4-83888 discloses a method of preventing the adherence of marine organisms by use of active ions generated by loading a DC current to an electrode body to perform electrolytic process of seawater. In addition, Japanese Patent Early publication No. 60-240775 discloses using an antifouling paint obtained by compounding a swellable high molecular material with rubber or synthetic resin as a ship's-bottom coating material.
However, even when using these techniques, it is difficult to perfectly prevent the adherence of marine organisms to the ship's body, screw, screw shaft, rudder and so on. In addition, some of the conventional antifouling paints for preventing the adherence of marine organisms give a bad influence on marine environment. Moreover, although the frequency of performing the cleaning operation of the ship can be decreased to a certain degree by preventing the adherence of marine organisms, it is still required to transport the ship to a dry dock after the long-term use of the ship and perform an operation of physically removing the adhered marine organisms. Since the operation of removing the adhered marine organisms from the ship transported to the dry dock is manual labor, the dock charge and the labor cost become a large burden. In particular, the removal of the marine organisms tightly adhered to the ship's body is a long-haul hard work. In addition, when the ship's-bottom coating material is removed together with the marine organisms, it leads to the occurrence of rust in the ship's body.
Therefore, it is expected to develop cleaning apparatus and method, which has the capability of removing marine organisms with ease and efficiency, while preventing damage to the painted surface of the ship's body, and reducing the cost required for the cleaning operation of the ship.